In order to increase the versatility of aircraft, proposals have been made to produce combi-aircraft, i.e., aircraft with one or more upper deck compartments that can be converted between passenger and cargo configurations. In order to accomplish this result, upper deck compartment(s) must be designed so that both passenger and cargo compartment requirements are met. One requirement of cargo compartments is that such compartments include a state of the art apparatus for extinguishing a fire in the compartment. State of the art cargo compartment fire extinguishing apparatus releases an inert gas, i.e., halogen, when a fire occurs. This requirement causes some difficulties in an upper deck cargo compartment due to the way aircraft airflow systems are designed. More specifically, in modern commercial aircraft pressurized air enters passenger compartments at the ceiling and exits via floor vents. Many "floor" vents are located at the base of the sidewall panels used to decorate the interior of the aircraft. After passing through the sidewall panels, the exiting air flows through holes formed in the aircraft deck, between the sidewall panels and the skin of the aircraft, into the cargo compartment located beneath the deck of the aircraft. Since pressure in the below deck cargo compartment is less than the pressure in the passenger compartment, normally, air always flows in this direction, i.e., from the above deck passenger compartment to the below deck cargo compartment. Air flows from the cargo compartment into the atmosphere outside the aircraft.
Merely adding an inert gas fire extinguishing system to a convertible compartment with the airflow path described above would create an ineffective system. Such a system would lose inert gas because the inert gas used in such systems, i.e., halogen, is heavier than air and sinks. Since the pressure differential between above deck passenger compartments and below deck cargo compartment pulls air from the bottom of the passenger compartment, the heavier halogen gas would rapidly be pulled from the convertible compartment to the cargo compartment. Such a dissipation of the inert (e.g., halogen) gas would either substantially decrease the effectiveness of the inert gas fire extinguishing system or require that the inert gas fire extinguishing system include substantially more gas than the minimum needed to extinguish a fire in the convertible compartment.
One suggested approach to alleviating the foregoing difficulty is to seal the sidewall panels (which are normally attached in a nonsealed manner) to their support structure and add a sealing dam between the sidewall panels and the skin of the aircraft, above the panel vents. In addition, a multitude of auxiliary valves, one associated with the vents in each panel were proposed. Since each valve was independently actuated, in order to convert the compartment from its normal (e.g., passenger) configuration to its cargo configuration, the individual actuation of a large number of valves (30 to 40) was required. In order to be absolutely certain that all valves were closed when the compartment was in its cargo configuration, the status of each valve was required to be individually determined. In addition, the closing of all of the sidewall vents resulted in a requirement that each panel be modified to have a blowout capability in the event of an explosive decompression in the cargo compartment. Because this approach requires an extensive modification of the sidewalls it is undesirably complex and expensive. Further, this approach is inherently unreliable due to the large number of valves that must be manually examined.
The present invention is directed to providing sidewall vent valves for convertible compartments located in the upper deck of an aircraft that avoid the foregoing difficulties.